This invention relates generally to new ester compounds, liquid crystal compositions containing the ester compound, methods of preparing the new ester compounds, and particularly to (2'-cyano-4'-n-alkylphenyl)-3-cyano-4-n-alkoxybenzoates.
Electro-optical display elements including liquid crystal compositions have been put into a variety of practical uses, in particular calculators, timepieces and the like. These liquid crystal display elements may be driven by various driving methods. A multiplexing drive is generally used to drive the liquid crystal displays, such as the generalized AC amplitudes selective mutliplexing method. However, such a method restricts the maximum number of rows which may be driven between eight and ten as a practical matter. Thus, there is difficulty in using the generalized AC amplitude selective multiplexing method to drive a television and a character display which are operated by addressing the multiplex matrix.
Recently, a method which takes advantage of the dielectric dispersion in the liquid crystal material has been found to be effective in elminating this disadvantage. However, when the multiplex matrix is addressed, by using the two-frequency matrix-addressing method, the energy consumption is high due to the fact that AC applied voltage is of high frequency and of high voltage. Thus, the two-frequency matrix-addressing method is less than completely satisfactory. It has been found that this energy consumption may be effectively reduced by making the driving voltage lower. It is known that the driving voltage V is dependent upon the dielectric anisotropy .DELTA..epsilon. of the liquid crystal material used. This relationship has been defined as ##EQU1## In other words, as the absolute value .vertline..DELTA..epsilon..vertline. increases, the value of driving voltage V is reduced.
Accordingly, it is desirable to provide a liquid crystal composition having the desired characteristics. Such a liquid crystal composition would have an increased absolute value of the negative dielectric anisotropy at frequencies higher than the critical frequency of lower than the critical frequency.